Process of shifting the double bond in mono-olefins to a terminal,non-tertiary position



March 11, 1969 w. D. HOFFMAN ETAL 3,432,570

PROCESS OF SHIFTING THE DOUBLE BOND IN MONO-OLEFINS TO A TERMINAL, NON-TERTIARY POSITION Filed Aug. 4, 1967 INVENTORS. WILLIAM D. HOFFMAN EMMETT H. BURK, JR

8 ROBERT M. EICHHORN' A TTORN E Yi United States Patent 3,432 570 PROCESS OF SHIFTING THE DOUBLE BOND IN MONO-OLEFINS TO A TERMINAL, NON- TERTIARY POSITION William D. Hotfman, Park Forest, Emmett H. Burk, Jr., Hazel Crest, and Robert M. Eichhorn, Chicago Heights, Ill., assignors to Sinclair Research, Inc., New York, N.Y., a corporation of Delaware Continuation-impart of applications Ser. No. 530,283, Feb. 28, 1966, and Ser. No. 127,917, July 31, 1961. This application Aug. 4, 1967, Ser. No. 658,320 US. Cl. 260683.2 22 Claims Int. Cl. C07c /28 ABSTRACT OF THE DISCLOSURE Terminal, non-tertiary, branched chain mono-olefins are prepared from other mono-olefins having the same carbon atom arrangement but having the olefinic bond in either an internal (i.e., non-terminal) location, or attached to a tertiary carbon atom, or both, by vaporizing and contacting the feed with HBr at a temperature of about 800 to 1050 F. Selective isomerization results, displacing the olefinic bond to a terminal, non-tertiary position. A preferred source of HBr for the reaction is tertiary alkyl bromide which disassociates at reaction temperatures to HBr and tertiary mono-olefins.

This application is a continuation-in-part of our copending application S.N. 530,283, filed Feb. 28, 1966, now abandoned, which, in turn, is a continuation-in-part of SN. 127,917, filed July 31, 1961, also abandoned.

This invention pertains to the production of terminal, non-tertiary, branched chain mono-olefins by selective carbon-to-carbon double bond isomerization of other different branched chained mono-olefins or mixtures containing such olefins. In a preferred embodiment, the invention is directed to the production of terminal, nontertiary mono-olefins by the isomerization of non-terminal, tertiary olefins. In another preferred embodiment, the invention is directed to the production of terminal, non-tertiary, quaternary carbon-containing mono-olefins by the isomerization of quaternary carbon-containing non-terminal mono-olefins.

Since the advent of the Ziegler method for polymerizing terminal olefins, there is a need for a general process for production of these olefin feedstocks. Although a typical refinery stream contains most of the various isoolefins such as 3-methylbutene-1 which might be raw materials for these polymers, the concentrations are generally quite low. One possible method for increasing the concentration of the desired raw materials is isomerization of other isomers to the desired one. Previous methods and catalysts for accomplishing this isomerization have suffered from various drawbacks such as lack of selectivity, sensitivity to impurities, trace halogen, etc.

Moreover, the equilibrium concentrations of the desired terminal, non-tertiary, branched chain mono-olefins in isomerization reaction products is frequently very low. In the isomerization of 2-methy1butene-l and -2 to 3- methylbutene-l, for instance, the equilibrium amount of desired olefin is usually of the order of about 5%. Consequently, it is evident why high selectivity is a necessary prerequisite in these types of isomerization reactions when it is desired to utilize the reaction on a commercial scale. Excessive by-product formation (including skeletal isomerization) in view of the small equilibrium concentrations of desired product renders such a process economically unacceptable.

It has been found that a terminal, non-tertiary,

branched chain mono-olefin may be produced by isomerizing, in the presence of HBr and under certain reaction conditions, other branched chain mono-olefins to cause selective migration of the double bond of such other olefins without excessive by-product formation and to produce an isomer mixture enhanced in terminal, nontertiary mono-olefin having the same carbon atom arrangement as the mono-olefin feed isomerized. By the term by-products, as used herein and in the claims, is meant all products made during the isomerization other than the desired terminal olefin and other monoolefins of the same carbon skeleton. The by-products include, for instance, the products produced by polymerization, cracking, skeletal isomerization (i.e., shifting of the branched chain), dehydrogenation, etc. The method of the invention may also exploit the low temperature reactivity of HBr and HCl with tertiary olefins before and/or after the isomerization to make an eminently practical procedure for the preparation of non-tertiary, terminal mono-olefins.

The feedstock isomerized may consist of any branched chain mono-olefin that is difierent than a terminal, nontertiary, branched chain mono-olefin, and, of course, which has a carbon atom arrangement, i.e., skeletal structure, which is capable of providing a terminal, nontertiary position for an olefinic bond. That is, the branched chain mono-olefin feed must possess at least one primary carbon atom bonded to a secondary carbon atom, like so: CH CH Also, it is to be understood that there cannot be quaternary carbon atoms interposed at any place along the carbon-to-carbon chains between the olefinic bond and the available terminal, non-tertiary site in the mono-olefin feedthe reason being, obviously, that the olefinic bond cannot be shifted past a quaternary carbon atom in the chain. The feedstock may, of course, comprise mixtures of branched chain mono-olefins. Thus, the branched chain mono-olefin feeds may be tertiary, non-tertiary, terminal or non-terminal olefins, or combinations thereof, other than a terminal, non-tertiary branched chain mono-olefin. Ordinarily, the mono-olefin feed will be a non-terminal branched chain olefin, but the invention contemplates feeding to the isomerization zone, for example, terminal, tertiary mono-olefins which undergo isomerization to subsequent non-terminal, tertiary monoolefins which upon subsequent recycle to the isomerization reaction can be converted to terminal, non-tertiary mono-olefins. The feedstocks may also contain other hydrocarbons, especially of the same number of carbon atoms or of similar boiling range. The branched chain mono-olefins have the branching desired in the final product and contain less than the equilibrium amount of the desired terminal mono-olefin on the basis of the total hydrocarbons passing to the reaction zone, e.g., fresh feed plus recycle. The branched chain olefin feeds of the invention have at least 5 carbon atoms and generally no more than about 14 carbon atoms, The branched chain mono-olefins may often be tertiary mono-olefins of 5 carbon atoms up to about 10 carbon atoms, characterized by having an absence of quaternary carbon atoms, or they may be quaternary carbon atom-containing mono-olefins of 7 to about 14, preferably 7 to about 10, carbon atoms. The process of the invention is very effective where the olefin feed to the isomerization is a mono-olefin having the general formula:

wherein R and R are alkyl, straight or branched chain, and R" is hydrogen when R has 1 carbon atom and hydrogen or R when R has more than 1 carbon atom.

Particularly preferred among the quaternary carboncontaining mono-olefins are olefin feedstocks of 7-14 carbon atoms of the type:

wherein R is a monovalent hydrocarbon radical, preferably alkyl.

The process of the invention may be used, for example, to make 3-methylbutene-1 from other methylbutenes; 4- methylpentene-l from other 4-methylpentenes; 3,4-dimethylpentene-l from other 3,4-dimethylpentenes; 4,4- dialkyl-l-alkenes from other 4,4-dialkylalkenes, etc. Advantageously where the isomerization feed produces undesired isomers, these isomers may be added to the feedstock to repress further formation of them.

The method of the present invention comprises subjecting vapors of the branched chain mono-olefin feedstock to contact with HBr at a reaction temperature of about 800 to 1000 F. or 1050 F., preferably about 850 to 950 F., for a time sufiicient to form a product having a weight ratio of terminal, non-tertiary, branched chain mono-olefin to by-products of at least 2:1, preferably at least 4:1. The branched chains in the terminal olefin product are in the same position as the branched chain mono-olefin feed. The effective amount of HBr used in the reaction may be at least about 0.01 mole, usually up to as much as about 0.75 or more mole per mole of branched chain mono-olefin feed but is preferably about 0.03 to 0.2 mole per mole. The total pressure for the isomerization may often range from about atmospheric to 1000 lbs. or more, preferably about 25 to 250 lbs.

The contact time employed in the method of the invention may be dependent upon the particular reaction temperature selected. For example, at a temperature of about 1050" F., the contact time employed may be at least 1 second up to about seconds. At reaction temperatures of 850 to 950 F. the contact time may be maintained at or below about seconds, while at reaction temperatures below 850 F. the contact time may be lengthened to about 30 seconds or even a minute, say, at about 800 F. In all events, the contact time employed, as aforementioned, is advantageously that sufficient under the reaction temperature utilized to provide a weight ratio of the desired terminal olefin to by-products of at least about 2:1, preferably at least 4:1. Also, the extent of conversion per pass of the feed will provide up to equilibrium conditions, which in the case of the quaternary carbon-containing feeds of the invention is often attained when 30% of the feed is converted, while in the case of tertiary olefin feeds of the invention equilibrium will often be reached after conversion of only about 10% of the feed. Thus, under the preferred reaction conditions, the process of the invention provides a selectivity to desired product of at least about 80%, often 90% or higher.

The reaction system is advantageously essentially devoid of water and oxygen, both of which decrease yield and give rise to corrosion. Likewise, a non-catalytic environment for the reaction is desirable, particularly in isomerization reactions wherein the equilibrium concentration is relatively small. Illustrative of non-catalytic vessels in which the isomerization may advantageously be conducted are those made of catalytically inert materials such as Pyrex glass, ceramic and high nickel-alloy reactors.

Unconverted feed from the isomerization, including, if desired, reaction products boiling in the same range as the desired product and higher, can be recycled to the isomerization zone. It is advantageous, for example, to include in the recycle feed mono-olefins other than the desired product but of the same skeletal structure as the desired product. The weight ratio of recycle feed to fresh feed will vary depending upon the mono-olefin feed isomerized. In the case of quaternary carbon-containing, mono-olefin feeds, the weight ratio of unconverted feed to fresh-feed can be at least about 2:1, preferably at least 3:1; while in the case of tertiary olefin feeds, the weight ratio can be at least 10:1, preferably at least about 15:1. Any means and techniques known in the art can be used for the separation of the desired olefin.

Tertiary olefins, that is, the olefins having a double bond at the tertiary carbon, may be easily removed from the other isomers in the reaction product by allowing the mixtures of isomers and halide to cool below about 200 F. and distilling non-tertiary olefins from the resulting tertiary alkyl halide. In order to facilitate this separation the reaction system can also contain HCl which adds to the tertiary olefin to form tertiary alkyl chlorides and thereby avoid having to supply excessive amounts of HBr over and above that needed to enhance the isomerization reaction. For example, the separation process is of particular utility in the case of isopentenes in which the isomerizate, before cooling in the presence of hydrogen halide, consists mainly of 3methylbutent-1 and the tertiary isoolefins 2-methylbutene-1 and 2-methylbutene-2, on a mono-olefin basis. Upon cooling this mixture of isomers and hydrogen halide, the halide reacts with the tertiary olefins to give a liquid mixture of 3-methylbutene-l and 2-methyl-2-halobutane from which the terminal olefin is easily recovered by distillation. The hydrogen halide may, if desired, contain up to about 99.5 or more percent of HCl based on the total of HCl and HBr. This preferred separation procedure, i.e., where the isomerizate is cooled in the presence of hydrogen halide to form halides of the tertiary olefins present, depends for its effectiveness upon addition of halogen to the least hydrogenated, that is, the tertiary, carbon atom of the olefin.

In the preparation of the isomerization feedstock, the high reactivity of hydrogen halide with a tertiary olefin may be exploited by first contacting a mixed olefin feedstock which contains tertiary olefin with anhydrous HBr, HCl or a mixture of HBr and HCl at below about 200 F, to form and separate tertiary alkyl halide. This tertiary alkyl halide, When vaporized and heated, produces a mixture of hydrogen halide and tertiary olefin eminently suited for isomerization by the method of this invention, providing HBr is present. Also, it is apparent that a tertiary alkyl halide, i.e., chloride and/ or bromide, from any source may be fed to our isomerization reaction to provide the tertiary olefin, as long as enough HBr is also present by separate addition or decomposition of alkyl halide to give the desired result in the reaction.

The invention, therefore, may be practiced in a commercial operation wherein a tertiary olefin feedstock may be recycled to extinction; namely, a tertiary olefin may be reacted with HBr, HCl or a mixture of HBr and I-ICl at below 200 F., the resulting tertiary alkyl halide vaporized to dissociate hydrogen halide, this mixture isomerized in the presence of HBr as described above and the mixture cooled to form tertiary alkyl halide from the tertiary olefin in the isomerizate. The olefin converted to non-tertiary isomers can be removed from the alkyl halide by distillation. The feedstocks to such a process may be, and usually are, mixtures of isoolefiins with other hydrocarbons and olefins of different types having the 8311116 approximate boiling range, as found, for example, in petroleum refinery distillate stocks. When such feeds are employed, the first step of the process, e.g., reaction with hydrogen halide at about room temperature up to about 200 F. to produce the tertiary alkyl halides from the olefins in the feed having double bonds at the tertiary carbon, may be followed by separation of the halide from unreacted hydrocarbons, for example, by distillation. The addition of halide to the olefin can be performed in the absence of solid catalysts. For olefins of the Z-methylbutene-l and Z-methylbutene-Z type, this reaction is very fast at room temperature. In this step the hydrogen halide may often be used in the ratio of about 0.1 to 5 moles per mole of tertiary olefin, preferably about 1 to 2 moles of hydrogen halide per mole of tertiary ole-fin. This reaction can be employed equally well to remove olefins of this type from dilute streams or with pure stocks, since the halide reacts slowly, if at all, with olefins not having the double bond at the tertiary carbon.

The remainder of the process, although theoretically divisible into parts, may actually occur automatically when these halides are heated to the reaction temperature and cooled. The decomposition of the halide becomes fast above its boiling point with the formation of gaseous hydrogen halides and olefins. A reaction in the gas phase results in the redistribution of the double bond in the olefin chain. The olefins are often present in the reaction zone in near-equilibrium concentrations. Then, upon cooling, the hydrogen halide once more reacts with the isoolefins having the double bond at the tertiary carbon to form tertiary alkyl halide while other types of olefins, e.g., desired non-tertiary terminal isoolefins, remain free.

A further operation may involve the separation of the desired olefin from the halide. This can be done by simple fractionation, which offers a big advantage over other systems. This provides an olefin concentrate which can then be used as is, or purified further. The halide fraction may be recycled back to the reaction zone in a mole ratio to fresh make-up feed as disclosed above.

Therefore, the process of this invention may comprise isomerization of vaporized olefins in the presence of HBr vapors, as previously described, and cooling the mixture to below about 200 F. to produce a mixture of terminal, non-tertiary isoolefin and tertiary alkyl halide. The vaporized olefin-hydrogen halide mixture may be produced by heating a tertiary alkyl halide to a temperature of about 200-400 F., and the tertiary alkyl halide in turn may be produced by subjecting isoolefins having a double bond at the tertiary carbon to preferably anhydrous HBr at a temperature from room temperature to about 200 F.

The invention will be better understood by reference to the accompanying drawing which is a schematic representation of apparatus suitable for performing the process of the invention but which should not be considered limiting.

The apparatus comprises a reactor which may be, for example, a tube 12 in an insulating jacket 15. The jacket may comprise, for example, an electric furnace but in any event it has a source for heating the reactor tube to the reaction temperature. The reactor 10 is connected by a line 18 to the reservoir 20 which holds the tertiary alkyl halide and also, usually, non-tertiary olefins, and is provided with means (not shown) to maintain a temperature between room temperature and about 200 F. The line 18 may be provided with pump 21. The reservoir 20 has an opening 22 for reception of olefin feed from any convenient source 25 and an opening 27 for reception of condensed reactor effluent from the line 28 and the condenser 30.

The reservoir 20 also is conveniently provided with an opening 33 which leads to a fractionator such as the overhead still 35. This fractionator is provided with a receptacle 38 for the desired olefin.

The following examples of the process of this invention are not to be construed as limiting.

Example I v A reservoir such as that in the drawing was charged with tertiaryamyl bromide prepared by reacting HBr with an isoamylene cut which had previously been extracted from a petroleum refinery stream. A slight amount of additional isoamylene was left in the bromide. The reactor was heated to 900 F. and the reservoir to 176 F. before flow was started through the rotameter pump. The feed rate was set at 228 ml./hr., which is equivalent to 1.8 moles bromide per hour. The conversion of the bromide to terminal olefin averaged between 3 to 6 g. per hour depending on the take-off rate used on the still. This corresponds to 43% to 86% of the theoretical amount possible. During the operation of the reactor, additional isoamylene was added occasionally to make up for the 3- methylbutene-l concentrate removed. The total operating time was 18 hours.

Example II A flask was flushed with nitrogen and 500 ml. of a C refinery stream added. The feed analyzed as: 26.9% isopentane, 5.9% n-pentane, 4.7% pentene-l, 19.6% pentene-2, 28.6% 2-methylbutene-2, 12.8% Z-methylbutene-l and 1.5% hexenes. The analysis showed no 3-methylbutene-l (2-methylbutene-3). HBr was added to the flask at about room temperature at the rate of about 0.26 mole/hr. until reaction ceased. The material boiling in the C range was removed by distillation; it analyzed 49.5% isopentane, 11.6% normal pentane; 7.9% pentene-l and 31.0% pentene-2. As can be seen, all the isoolefins originally present in the fed were converted to higher boiling bromides. Small amounts of the normal olefins also reacted. The bromide fraction was then distilled, with the bromide fraction boiling approximately at 107 C.

The mixed bromides fraction was passed through a glass reactor at a LHSV of 1.8 cc. feed/cc. reactor volume and a temperature of 950 F. After the reaction was finished, the product mixture was cooled and the olefins were removed by distillation and analyzed by gas chromatography. It was found that the olefin portion contained 40% 3-methylbutene-1. The bromide portion was recycled to the reactor to produce an olefin product comprising almost 3-methylbutene-l.

Example III The reservoir of the drawing was charged with a mixture containing 70 mole percent 2-bromo-2-methylpentane and 30 mole percent 4-methylpentene-2. The reactor was brought to temperature and the run began. The conditions are as follows:

Feed rate to reactor cc./hr. 228 Reactor temperature F 940-950 Reservoir temperature C 79 Overhead still temperature F Component 30 min. 1 hour 2 hours 2% hours 2-methylpentane 2. 5 1.8 l. 1 0.8 4-methylpentene-1 10.0 12. 3 17. 7 21. 2 Cis 4-methy1pentene-2. 37. 5 32. 0 23. 5 20. 7 Trans 4-methylpentene-2 50.0 54. 0 57. 7 54. 0 2rnethylpentene-1 1. 0 2-methylpentene2 2. 5

It was found necessary to add about 100 cc. of 2- methylpentene-Z in order to contain the HBr in the reactor system. It will be noted that a small amount of this material is present in the overhead product. This product can be used for feed to a still to make high purity 4-methylpentene-1.

Examples IV-IX A series of runs was carried out using HBr as a catalyst for the isomerization of iso C olefins to 4-methyl entene-l. The feed consisted of 0.7 mole 2-bromo-2-methylpentane and 0.3 mole of 4-methylpentene-2. This is approximately the recycle feed composition. The experiments were run in a Vycor reactor packed with glass beads. The free volume was approximately 25 cc. The results of the work are shown in Table I below.

TABLE I Feed Rate Percent Percent Temp, F. (cc./hr.) Liquid 4-metliyl- Recovered pentene-l Example:

The remainder of the liquid product other than 4-methylpentene-l in the' olefin portion of the reaction product is mainly cis and trans 4-methylpentene-2. No other carbonisometric C olefins were detected. As can be seen in Table I, the amount of l-olefin varies between 15 to 18% based on the olefin in the reaction product.

Examples X-XIV In the following examples, mixtures of isoamylene with minor amounts of t-amyl bromide were fed to a reactor consisting of a coil of A" Inconel tubing having a volume of 260 cc.

Example X XI XII XIII XIV Feed (moles/hr.):

t Amyl bromide 0.63 0. 32 0. 11 0.23 1. 49 Isoamylenc 11. 95 17. 5 6. 36 2. 5 16. 32 Temp., F 950 950 950 800 950 Mole traction HBr in vapor. 0477 0.018 0.017 0. 077 0. 077 Pressure, p.s.i.g 100 100 100 100 135 Contact time, sec 9. 0 6. 18.0 43. 2 7. 7 Approach to equilibrium, percent... 95. 3 47. 5 77.0 91 100 Thus, where a higher pressure of HBr is employed (Example XIV) at a temperature of about 950 F., a very favorable conversion was achieved even at a very short contact time. Example XIII shows that where lower temperatures are employed, longer contact times generally are needed.

Examples XV and XVI In the following examples an isoamylene feed containing 0.6% by weight t-butyl bromide and 4.92% by weight t-amyl bromide was isomerized using the procedure and reaction of Examples X-XIV. The feed analyzed as follows:

The isomerization conditions and results are summarized in the following table.

ISOAMYLENE FEED ISOMERIZATION Example IV XVI Reaction temp, F 900 900 Contact time, sec. Feed rate, lbs./hr 100 100 Test run, hrs 20 20 Yield of 3-methylbutene-1, lbs. (total). 59. 3 62. G Selectivity to 3-methylbutenc-1, percent 1 81 1 82 Yield of material boiling at and above 400 F., based on yield of 3-mcthylbutene-1, percent 1 15.7 1 14.4 Yield of C4 and lighter materials based on yield of 3- methylbutcnc-l, percent 1 0.1 1 8. 0 Approach to equilibrium, based on mass balance, percent 88 00 Predicted approach, percent 86 Yield of isopentane, based on yield of 3-methylbutenc-l, percent 3. 5 4. 5 Percent of material boiling at and above 400 F., per

pass 0.465 0. 45 Percent of C4 and lighter materials, per pass 1 0. 27 1 0. 27

1 Based on material balance (mass). Definitions:

Yield of matl. boiling at and lbs. of matl. made above 400 F., based on yield of =-X 3-1ncthylbutenc-1 lbs. of B-mctylbutane-1 made Yield 01 C and lighter mat/1., lbs. of matl. made based on yield of 3-1ncthyl- 100 butenc-l, percent lbs. of 3-mcthylbutene-l made lbs. of 3-mcthy1butcnc-1 made Approach to equilibrium, percent lbs. of C5 isoolefins in feed (total) --X 100 Percent of 3-methy1- butene-l in equilibrium mixture of C isoolefins During the isomerization, a portion of the reaction product mixture, after removal of desired product and lower boiling by-products, was recycled to the isomerization in a weight ratio of reaction product mixture to fresh feed of approximately 20: 1. The recycle feed had the following typical analysis:

Recycle feed,

The data demonstrate the high selectivity to 3-methylbutene-l obtained by the process of the invention.

Example XVII A feedstock comprising mostly trans-4,4-dimethylpentene-2 was prepared by alklation of propylene with t- .butylchloride, followed by pyrolysis, to give a mixture containing 25% 4,4-dimethylpentene-l and 75% 4,4-dimethylpentene-2. This was distilled over sodium and fractionated to remove most of the 4,4-dimethylpentene-l.

A small glass reactor (12.6 cc. free volume), was filled with glass beads and aged by passing 0,, bromides over the beads at temperatures from 800 to 950 F. A mixture of 0.1 mole of t-butyl bromide and 0.1 mole of the 4,4-dimethylpentene-2 was then passed through this rer actor at a temperature of 950 F. and a LHSV of 1. After 6.8 g. of feed had been consumed, the run was terminated and 6.65 g. of product collected. The product was found to consist of isobutylene, C olefins and t-butyl bromide. The composition of the C olefins was as follows: 21.8% 4,4 dirnethylpentene 1; 71.0% trans-4,4-dimethylpentene-2; and 7.3% cis-4,4-dimethylpentene-2.

The above run was repeated using t-butyl chloride in place of t-butyl bromide. The concentration of 4,4-dimethylpentene-l was increased from 4.6% in the feed to only 5.7% in the product, and the amount of the cis isomer from 2.6 to 6.5%. Thus HCl is a much poorer catalyst than HBr.

It is claimed:

1. A process for selectively converting branched chain mono-olefin of to about 14 carbon atoms, which is other than a terminal, non-tertiary mono-olefin, to terminal, non-tertiary mono-olefin having the same carbon atom arrangement as the olefin converted which comprises contacting in a reaction zone a vaporized feed comprising (a) said branched chain mono-olefin and less than an equilibrium amount of (b) said tenminal, nontertiary mono-olefin at a temperature of about 800 to 1050 F. with at least about 0.0 1 mole of HBr per mole of said branched chain mono-olefin in said feed, separating terminal, non-tertiary mono-olefin product from the resultant reaction mixture, and recycling unconverted feed to the reaction zone.

2. The process of claim '1 wherein the reaction mixture, after said contacting with HBr, is cooled in the presence of hydrogen halide selected from the group consisting of HBr, HCl and mixture of HBr and HCl to below about 200 F. to effect selective hydro-halogenation of tertiary olefin present in the reaction mixture, and non-tertiary olefin present in the cooled mixture is separated therefrom.

3. The process of claim 2 wherein said hydro-halogenated tertiary olefin is combined with fresh said branched chain mono-olefin-containing feed in a weight ratio of hydro-halogenated tertiary olefin to fresh feed of at least about :1 and the combined feed is recycled to the reaction zone.

4. The process of claim 3 wherein the HBr is supplied to the reaction zone as a tertiary alkyl bromide which when heated to said contacting temperature disassociates to yield HBr and tertiary mono-olefin.

-5. The process of claim 4 wherein the branched chain mono-olefin being converted is a tertiary mono-olefin.

6. The process of claim 5 wherein said tertiary alkyl bromide is the bromide of the tertiary mono-olefin being converted.

7. The process of claim *5 wherein the tertiary monoolefins being converted is a tertiary mono-olefin of 5 to about 10 carbon atoms having the general formula:

wherein R and R are alkyl and R" is hydrogen when R has 1 carbon atom and is hydrogen or R when R has more than 1 carbon atom.

8. The process of claim 7 wherein the contacting of vaporized feed with HBr is for a time sufficient to convert up to about 10% of the tertiary mono-olefin being converted and to provide a reaction mixture containing a weight ratio of (b) to by-products other than the desired terminal olefin and other mono-olefins of the same carbon skeleton of at least about 2:1.

9. The process of claim 8 wherein the tertiary monoolefin being converted is 2-methylbutene-2 and the terminal, non-tertiary mono-olefin conversion product is 3- methylbutene-l.

10. The process of claim 8 wherein the contacting temperature is about 850 to 950 F., the molar ratio of HBr to said tertiary mono-olefin is about 0.03 to 02:1, the contact time is suflicient to provide a reaction mixture containing a weight ratio of (b) to by-products other than the desired terminal olefin and other mono-olefins of the same carbon skeleton of at least about 4:1, and, in the combined feed for recycle, the weight ratio of hydrohalogenated tertiary olefin to fresh feed is at least about 15:1.

11. A process for selectively converting Z-methyl-butene-2 to 3-methylbutene-1 which comprises contacting in a reaction zone a vaporized feed comprising (a) 2- methylbutene-2 and less than an equilibrium amount of (b) 3 methylbutene-1 at a temperature of about 850 to 950 F. with about 0.08 to 0.2 mole of HBr per mole of 2-methylbutene-2 in said feed for a time sutficient to convert up to about 10% of said 2-methylbutene-2 and to provide a reaction mixture containing a weight ratio of 3-rnethylbutene-l to by-produ'cts other than 3-methylbutene-l and other mono-olefins of the same carbon skeleton of at least about 4:1; removing the reaction mixture from the reaction zone;

cooling the mixture in the presence of hydrogen halide selected from the group consisting of HBr, HCl, and mixtures of HBr and HCl to below about 200 F. to effect selective hydrohalogenation of unconverted 2-methylbutene-2;

separating said 3-methylbutene-1 from the cooled mixture by distillation;

combining said hydrohalogenated, unconverted 2- methylbutene-2 with fresh said 2-methylbutene-2- containing feed in a weight ratio of hydrohalogenated, unconverted Z-methylbutene-Z to fresh feed of at least about 15:1; and

recycling the combined feed to the reaction zone.

12. The process of claim 11 wherein the HBr is supplied to the reaction zone as tertiary amyl bromide which disassociates at said contacting temperature to yield HBr and tertiary amylene.

13. A process for selectively converting quaternary carbon atom-containing, non-terminal mono-olefin of 7 to about 14 carbon atoms to a terminal, non-tertiary monoolefin having the same carbon atom arrangement as the olefin converted which comprises contacting in a reaction zone a vaporized feed comprising (a) said non-terminal mono-olefin and less than an equilibrium amount of (b) said terminal mono-olefin at a temperature of about 800 to 1050 F. with at least about 0.01 mole of HBr per mole of said non-terminal mono-olefin in said feed, separating terminal mono-olefin product from the resultant reaction mixture, and recycling unconverted feed to the reaction zone.

14. The process of claim 13 wherein the HBr is supplied to the reaction zone as a tertiary alkyl bromide which when heated to said contacting temperature disassociates to yield HBr and tertiary mono-olefin.

15. The process of claim 14 wherein the reaction mixture, after said contacting with HBr, is cooled in the presence of hydrogen halide selected from the group consisting of HBr, HCl and mixtures of HBr and HCl to below about 200 F to effect selective hydrohalogenation of tertiary olefin present in the reaction mixture, and said terminal, non-tertiary mono-olefin present in the cooled reaction mixture is separated therefrom, leaving a residual mixture.

16. The process of claim 15 wherein said residual mixture is combined with fresh said non-terminal monoolefin-containing feed in a weight ratio of residual mixture to fresh feed of at least about 2:1 and the combined feed is recycled to the reaction zone.

17. The process of claim 16 wherein the quaternary carbon atom-containing, non-terminal mono-olefin being converted has the general formula:

i R(3C=CCHa wherein R is alkyl.

18. The process of claim 17 wherein the quaternary carbon atom-containing, non-terminal mono-olefin being converted is 4,4-dimethylpentene-2 and the terminal mono-olefin conversion product is 4,4-dimethylpentene-1.

19. The process of claim 17 wherein the contacting of vaporized feed with HBr is for a time sufficient to convert up to about 30% of the non-terminal mono-olefin being converted and to provide a reaction mixture containing a weight ratio of (b) to by-products other than the desired terminal olefin and other mono-olefins of the same carbon skeleton of at least about 2:1.

20. The process of claim 19 wherein the contacting temperature is about 850 to 950 F., the molar ratio of HBr to said non-terminal mono-olefin is about 0.03 to 02:1, the contact time is sufficient to provide a reaction mixture containing a weight ratio of (b) to by-products of at least about 4:1 and, in the combined feed for recycle, the weight ratio of residual mixture to fresh feed is at least about 3:1.

21. A process for selectively converting 4,4-dimethylpentene-2 to 4,4-dimethylpentene-l which comprises contacting in a reaction zone a vaporized feed comprising (a) 4,4-dimethylpentene-2 and less than an equilibrium amount of (b) 4,4-dimethy1pentene-1 at a temperature of about 850 to 950 F. with about 0.03 to 0.2 mole of HBr per mole of 4,4-dimethylpentene-2 in said feed for a time sufiicient to convert up to about 30% of said 4,4-dimethylpentene-2 and to provide a reaction mixture containing a weight ratio of 4,4-dimethylpentene-1 to by-products other than 4,4-dimethylpentene-1 and other mono-olefins of the same carbon skeleton of at least about 4:1; said HBr being supplied to the reaction zone as a tertiary alkyl bromide which when heated to said contacting temperature disassociates to yield HBr and tertiary mono-olefin; removing the reaction mixture from the reaction zone; cooling the mixture in the presence of hydrogen halide selected from the group consisting of HBr, HCl, and mixtures of HBr and HCl to below about 200 F. to elfect selective hydrohalogenation of tertiary olefin present in the reaction mixture; separating said 4,4-dimethylpentene-1 from the cooled mixture, leaving a residual mixture; combining said residual mixture with fresh said 4,4-

dimethylpentene-Z-containing feed in a weight ratio of residual mixture to fresh feed of at least about 3:1; and recycling the combined feed to the reaction zone. 22. The process of claim 21 wherein the HBr is supplied to the reaction zone as tertiary butyl bromide which disassociates at said contacting temperature to yield HBr and isobutylene.

References Cited UNITED STATES PATENTS 2,368,446 1/1945 Bue 260-677 2,156,070 4/1939 Stern 260-677 2,403,439 7/1946 Ipatietf et a1. 260683.2 2,404,927 7/1946 Schmerling et a1. 260-677 3,227,770 1/1961 Burk et a1. 260-677 DELBERT E. GANTZ, Primary Examiner.

V. OKEEFE, Assistant Examiner. 

